Telephone system



March s, 1927. 1,620,090

A. FLAD TELEPHONE SYSTEM Filed April 225r 1926 Patented Mar. 8, 1927..

STATES P 1 i l i" AETUE ELAD, or BERLIN, GERMANY, 'AssrGNon fro srEivrENs a' EALSKE, Ait'rrEN- GESELLSCHAFT, wEnNERwEi-trr, or sIEr/rENssfrAnr, NEAEBERLIN, GERMANY.

TELEPHONE SYSTEMS.

Application led April 23, 1926, Serial No. 104,022, and in- Germany .Tune 27, 1925.

The present invention relates to a circuit arrangement for testing lines, especially in telephone systems, and it consists in that, when the test relay is connected to the line to be tested it is caused to operate by the chargingor discharging current of a capacity.

The arrangement according to the invention Vhas important advantages over the known arrangements for testing the lines. For example, it enables the test relay to operate with the required speed even when the lines to be tested are of such length that their electricalr properties considerably eX- tend the time taken for the test relay to attract its armature in the known arrangement.

The drawing shows several methods of carrying out the invention.

The Figures 1 and 2 show arrangements for systems with automatic operating, and Figurey 3 shows an arrangement with manual working.

In the example shown in the Figure 1, a

' group selector is indicated. It is presumed `to be a Strowger switch of known type, but only those parts are shown that are required for understanding the invention, these comprise the impulse receiving relay A1, which is under the control of the calling party, the releasing relay V1, as well as the circuit of the rotary magnet D1 and the testing relay P1. Y

When the switch is taken into use, the impulse relay Ad` is energized in the microt phone circuit of the calling party, and at its Contact 1651 connects up the slow releasing release relay V1. The latter, among other circuit changes` closes its contacts 2111 and 3111, thereby on the one hand preparing the circuit for the rotary magnet D1 and on the other hand connecting the test relay P1 to the test wiper 4. The circuit of the rotary magnet D1 can in known manner be closed only when a not shown steering relay has fallen back and has closed its contact 5ft/1 at the ond of the train of impulses for lifting the group selector to the required level. during which train of impulses the steering relay is energized. The circuit for the rotary magnet D1is then closed as follows: earth. oif normal contact 6k, contacts 2o1, 502, 7291, rotary magnet D1, self inter rupting Contact 8011, battery, earth. The switch is moved step by step over the contacts in the selected level. and it is arrested in the manner hereafter described when the test wiper l1 reaches the test contact of an reaches. the test contact of an idle line, which may be assumed to be the line shown in Fig. 1. the condenser 9 of this line is discharged over the following route: condenser 9, test contact 11, test wiper 11, contact 31121, relay P1, earth. This discharge current causes the relay P1 to operate quickly and it then locks itself over a part of the charging circuit for the condenser: earth, battery1 relay HB1, test lead 10, test contact 11` test wiper 4, Contact 3121, relay P1, earth. `When the discharge circuit is closed, the relay P1 operates immediately, at the contact '7101 it opens the circuit of the rotary magnet D1 and among other circuit changes it switches through the speaking leads at the contacts 12291 and 13291.

After the condenser 9 has been discharged, it is slightly charged again'. over the charging` circuit; but by suitably adjusting the resistances of the relay'HR1 and of the test relay P1 and the corresponding relays of all other lines, the discharge current 'is prevented from attaining a magnitude suiiicient to operate the test relay of a testing switch when the switch reaches the test Contact of an engaged line. rThus the seized line is marked Engaged without requiring the switch, which has been marked Engaged, to

perform speci-al switching operations, such as short circuiting a winding.- It should also be mentioned that it would be impossible for the test relay P1 to be operated over the test lead and the relay HB1 without the condenser discharge, but that the test relay can keep its armature attracted over this circuit after it has been energized.

Fig. 2 shows an. arrangement, in which the test relay is caused to be operated by the current that charges a capacity. The condenser 19 is connected to the same potential l(batt-ery) as the relay HRZ located in the test lead 20. Thus the condenser is discharged. When the test wiper 14 of a testing switch now reaches the test contact 21,

the following charging circuit is then closed: earth, testlrelay P2, contact 22113, which corresponds to the Contact Bcl in F ig. 1, test wiper 14, Contact 21, condenser 19, battery, earth. This charging current causes the relay P2 to operate at once, and it then locks itself over the test lead 2O and the relay HB2.

When the test wiper of a hunting switch reaches the test contact of an engaged line,

Y the test relay of that switch, similarto relay P2 cannot be energized because a charging current cannot become suliiciently large to energize the relay.V

` The Figure 8 shows how the arrangementshown in Figurel can Vbe applied to a manual system. After the plug S has been inserted into the jack Jl, the relay P3 lan only operate when the line, which is connected to the plugged jack, is free. In that case the condenser 29 is charged and a strong discharge current functions over the following route: earth, relay P3, plugrcontact 24C, bush 31 of the j ack, condenser 29. Thereupon the relay P3 closes both the contacts 32293 and 33203, thus switching through the speaking leads. If the plug is inserted into the jack of an engaged line, the relay Pa cannot operate, because a discharge current of the Vrequired magnitude cannot pass.

In the examples shown, the test relays P1, P2 and P3 are provided only with one winding. It is obvious that the arrangement can bel such that the test relay has two windings connected in series, of these a high resistance winding is short circuited when the relay is operated.

Y What is claimed is: v

1. In a telephone system, a trunk line, a condenser connected to the test conductor'of said trunkline, a circuit for charging said condenser, and a test relay initially Venergized in series with said condenser and maintained energized thereafter over a section of said charging circuit.

2. In a telephone system, an automatic switch, trunk lines terminating in the banks of said switch, a condenser connected to the test Contact of each trunk line, a circuit for each line for charging the associated conof a line when said switch is operated to i connect with an idle line, said condenser being discharged thereby to mark said trunk line busy.

3. In a telephone system, a trunk line, a

vcondenser connected to the testconductor of said trunk, means for charging said con denser ylo a certa-1n potential to mark said trunk line idle, and means for reducing said potential to mark said trunk line busy.

Ll. In a telephone system, a trunk line, a condenser associated with said trunk line, means for charging said condenser to mark said trunk line idle, and means for reducing the charge on said condenser to mark said trunk line busy.

5. In a telephone system, an automatic switch, a trunk line, a condenser connected to the test conductor of said trunk line, a

charging circuit for said condenser, said trunk line being marked Busy or Idle depending on the potential to which said condenser is charged, a test relay, means for connecting said test relay to said test conductor,y said relay thereupon actuating or remaining deactuated depending upon whether said line is idle or busy, said relay being maintained energized thereafter over a sec-tion of said charging circuit and the potential to which said condenser is charged being changed to mark said trunk line busy providing said relay is actuated.

6. In a telephone system, a trunk line, a test relay, means for connecting said relay Vto the near end of the test conductor of said trunk line, a source of current at the far end of said test conductor, and a condenser connected to the near end of said test conductor for storing energy and for facilitating the quick operation of said test relay when it is connected to said test conductor.

In witnessfwhereof, I hereunto subscribe my name this 31st day of March, A. D. 1926.

ARTUR FLAD. 

